My strategy for a trip like this is to get up early the day I depart the US. Then I hit the lounge for a few drinks before the flight. I enjoy the lunch service with wine and cocktails. I usually watch a movie and once the first movie ends I wash up and take an Ambien and sleep. I usually wake up an hour or 2 before landing. Then stay awake for the flight to SIN (it is 7 hours from NRT). I usually can't sleep right away at the hotel but try to go to bed by 3am SIN time. Again an Ambien helps here. Then when I wake up I am usually fine for the duration of the trip.